Explication de la requête multi-conditions dans MyBatis-javaDidacticiel-php.cn

Un : Utiliser du SQL dynamique pour compléter une requête multi-conditions

a : Utiliser if+where pour implémenter une requête multi-conditions

Tout d'abord, les exigences du scénario, il y a une note et la table de classes, la première exigence est une requête conditionnelle basée sur le nom et l'âge de la requête floue, la méthode de la couche d'interface

 public  List<student>  getStudentByIf(student stu);

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Vient ensuite la configuration du fichier de mappage

 <select id="getStudentByIf" parameterType="stu" resultType="stu">select * from student       <where>   <if test="stuAge!=0">   and stuAge>#{stuAge}       </if> <if test="stuName!=null"> and stuName LIKE &#39;%&#39; #{stuName} &#39;%&#39;             </if>   </where></select>

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Test

 studentDao dao = MyBatis.getSessionTwo().getMapper(studentDao.= "z"List<student> list="----------"+

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---- ------zhangyu<br/>---------zy<br/>----------zy<br/>----------zhang

 <br/>

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b : choisir quand la classification

Cette méthode est la même que le principe de structure de boucle de choix en Java Pour juger plusieurs situations, il suffit de modifier le. fichier de mappage

Classe d'interface

  public List<student> getAllStudentByLike(Map<String, Object> userMap);  //使用map作为参数

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Fichier de mappage

 <span style="color: #0000ff"><</span><span style="color: #800000">select </span><span style="color: #ff0000">id</span><span style="color: #0000ff">="getAllStudentByLike"</span><span style="color: #ff0000"> parameterType</span><span style="color: #0000ff">="Map"</span><span style="color: #ff0000"> resultType</span><span style="color: #0000ff">="stu"</span><span style="color: #0000ff">></span><span style="color: #000000">select * from student</span><span style="color: #0000ff"><</span><span style="color: #800000">where</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">choose</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">when </span><span style="color: #ff0000">test</span><span style="color: #0000ff">="stuName!=null"</span><span style="color: #0000ff">></span><span style="color: #000000"> stuName like CONCAT(&#39;%&#39;,#{stuName},&#39;%&#39;)</span><span style="color: #0000ff"></</span><span style="color: #800000">when</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">when </span><span style="color: #ff0000">test</span><span style="color: #0000ff">="stuAge!=0"</span><span style="color: #0000ff">></span><span style="color: #000000"> stuAge> #{stuAge}</span><span style="color: #0000ff"></</span><span style="color: #800000">when</span><span style="color: #0000ff">><br/></span>

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<otherwise>
    1=1
</otherwise>

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<span style="color: #0000ff"><br/></span><span style="color: #0000ff"></</span><span style="color: #800000">choose</span><span style="color: #0000ff">></span><span style="color: #0000ff"></</span><span style="color: #800000">where</span><span style="color: #0000ff">></span><span style="color: #0000ff"></</span><span style="color: #800000">select</span><span style="color: #0000ff">></span>

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Résultat

zhangyu
zy
zy
zhang

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c : Il y a trois façons à utiliser foreach pour compléter des requêtes complexes,

Le premier type : Le paramètre entrant est un type tableau

🎜>

//传一组 xueshengID public List<student> getStudentBystuId_foreach_array(Integer[] ints);




映射文件配置 <!--跟据学生id查询学生Interger-->
    <select id="getStudentBystuId_foreach_array" resultMap="studentList">select * from student<if test="array.length>0">where stuId IN/*数组形式传入学生Id*/<foreach collection="array" item="stu" open="(" separator="," close=")">  #{stu}</foreach>
        </if>
    </select>

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Le deuxième type : passer dans la collecte de liste

  Integer[] ints = {2,3,4};
        List<student> list = dao.getStudentBystuId_foreach_array(ints);for (student item:list) {
            System.out.println(item.getStuName());
        }

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   public List<student> getStudentBystuId_foreach_list(List<Integer> list);

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Test :

  <!--跟据学生id查询学生list方式--><select id="getStudentBystuId_foreach_list" resultMap="studentList">select * from student<if test="list.size>0">where stuId IN
        /*集合形式传入学生Id*/<foreach collection="list" item="stu" open="(" separator="," close=")">#{stu}</foreach></if></select>

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Le troisième type : Définir selon la carte

 studentDao dao = MyBatis.getSessionTwo().getMapper(studentDao.class);
        Integer ints = 2;
        List<Integer> list = new ArrayList<Integer>();
        list.add(ints);
        List<student> stulist = dao.getStudentBystuId_foreach_list(list);
        for (student item:stulist) {
            System.out.println(item.getStuName());
        }

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Pour imprimer les résultats, vous pouvez procéder comme suit.

 public List<student> getStudentBystuId_foreach_map(Map<String, Object> stuMap);

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d ; Deux méthodes d'implémentation d'un à plusieurs

Principalement en raison de différentes configurations dans resultMapper

Méthodes d'interface

 <!--跟据学生id查询学生map方式--><select id="getStudentBystuId_foreach_map" resultMap="studentList">select * from student where stuId IN
        /*集合形式传入学生Id*/<foreach collection="stuId" item="stu" open="(" separator="," close=")">    <!--collection是自己定义的，就是map的key值-->#{stu}</foreach></select>

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<span style="color: #008000">  Map<String ,Object> stumap = new HashMap<String, Object>();
        List<Integer> listStuId = new ArrayList<Integer>();
        listStuId.add(2);
        listStuId.add(3);
        listStuId.add(4);
        stumap.put("stuId",listStuId);
         List<student> list = dao.getStudentBystuId_foreach_map(stumap);
        for (student item:list
             ) {
            System.out.println(item.getStuName());
        }</span><span style="color: #008000"><br/></span>

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Configuration du fichier de mappage

 public grade getGradeById(int gradeId);

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 <span style="color: #008000"><!--</span><span style="color: #008000">实现一 对多的第一中实现</span><span style="color: #008000">--></span><span style="color: #0000ff"><</span><span style="color: #800000">resultMap </span><span style="color: #ff0000">id</span><span style="color: #0000ff">="gradeMapOne"</span><span style="color: #ff0000"> type</span><span style="color: #0000ff">="grade"</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">id </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="gradeId"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="gradeId"</span><span style="color: #0000ff">></</span><span style="color: #800000">id</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">result </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="gradeName"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="gradeName"</span><span style="color: #0000ff">></</span><span style="color: #800000">result</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">collection </span><span style="color: #ff0000">property</span><span style="color: #0000ff">="gatStudent"</span><span style="color: #ff0000"> ofType</span><span style="color: #0000ff">="stu"</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">id </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="stuUd"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="stuId"</span><span style="color: #0000ff">></</span><span style="color: #800000">id</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">result </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="stuName"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="stuName"</span><span style="color: #0000ff">></</span><span style="color: #800000">result</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">result </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="stuAge"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="stuAge"</span><span style="color: #0000ff">></</span><span style="color: #800000">result</span><span style="color: #0000ff">></span><span style="color: #0000ff"></</span><span style="color: #800000">collection</span><span style="color: #0000ff">></span><span style="color: #0000ff"></</span><span style="color: #800000">resultMap</span><span style="color: #0000ff">></span><span style="color: #008000"><!--</span><span style="color: #008000">实现一 对多的第二中实现</span><span style="color: #008000">--></span><span style="color: #0000ff"><</span><span style="color: #800000">resultMap </span><span style="color: #ff0000">id</span><span style="color: #0000ff">="gradeMap"</span><span style="color: #ff0000"> type</span><span style="color: #0000ff">="entity.grade"</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">id </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="gradeId"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="gradeId"</span><span style="color: #0000ff">></</span><span style="color: #800000">id</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">result </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="gradeName"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="gradeName"</span><span style="color: #0000ff">></</span><span style="color: #800000">result</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">collection </span><span style="color: #ff0000">property</span><span style="color: #0000ff">="gatStudent"</span><span style="color: #ff0000"> ofType</span><span style="color: #0000ff">="student"</span><span style="color: #ff0000"> select</span><span style="color: #0000ff">="getStudentById"</span><span style="color: #ff0000"> column</span><span style="color: #0000ff">="gradeId"</span><span style="color: #0000ff">></</span><span style="color: #800000">collection</span><span style="color: #0000ff">>    <!--column的值主要作为下次查询的条件，既查询学生的条件--></span><span style="color: #0000ff"></</span><span style="color: #800000">resultMap</span><span style="color: #0000ff">><br/></span>

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Les deux méthodes peuvent être réalisées, imprimer Effet

    <select id="getGradeById" resultMap="gradeMapOne">select * from grade,student where grade.gradeId = student.stuGrade and gradeId = #{gradeId}</select><!--ddddddddddddddddddd--><select id="getGradeById" resultMap="gradeMap">select * from grade where gradeId=#{gradeId}</select><select id="getStudentById" resultType="entity.student">select * from student where stuGrade = #{stuGrade}</select>

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Effet d'impression du plan 1

<br/>

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==> Préparation : sélectionnez * from grade,student où grade.gradeId = student.stuGrade et gradeId ======== = ===A sql

==> Paramètres : 1(Integer)

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<== Colonnes : gradeId, gradeName, stuId, stuName, stuAge, stuGrade 🎜><== Rangée : 1, S1297 , 2, zhangyu, 19, 1

<== Rangée : 1, S1297, 3, zy, 20, 1

<== Rangée : 1, S1297, 4, zy, 21, 1

<== Total : 3

zhangyu

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  @Testpublic void  TestConn(){
       gradeDao dao = MyBatis.getSessionTwo().getMapper(gradeDao.class);

       grade grade = dao.getGradeById(1);       for (student item:grade.getGatStudent()            ) {
           System.out.println(item.getStuName());
       }

    }

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Option 2 effet d'impression

== > Préparation : sélectionnez * dans la classe où gradeId=? gradeName

<== Ligne : 1, S1297

====> ====Le deuxième sql

= ===> Paramètres : 1(Long)

<==== Colonnes : stuId, stuName, stuAge, stuGrade

<==== Row : 2, zhangyu, 19, 1
& lt; ==== rangée : 3, zy, 20, 1
& lt === rangée : 4, zy, 21, 1
& lt; ; ======== == Total : 1
zhangyu
zy
zy

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